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cae87e64 | 1 | /* Memory allocation next to an unmapped page. |
d614a753 | 2 | Copyright (C) 2017-2020 Free Software Foundation, Inc. |
cae87e64 FW |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
cae87e64 FW |
18 | |
19 | #include <support/check.h> | |
20 | #include <support/next_to_fault.h> | |
21 | #include <support/xunistd.h> | |
22 | #include <sys/mman.h> | |
23 | #include <sys/param.h> | |
24 | ||
25 | struct support_next_to_fault | |
26 | support_next_to_fault_allocate (size_t size) | |
27 | { | |
28 | long page_size = sysconf (_SC_PAGE_SIZE); | |
29 | TEST_VERIFY_EXIT (page_size > 0); | |
30 | struct support_next_to_fault result; | |
31 | result.region_size = roundup (size, page_size) + page_size; | |
32 | if (size + page_size <= size || result.region_size <= size) | |
33 | FAIL_EXIT1 ("support_next_to_fault_allocate (%zu): overflow", size); | |
34 | result.region_start | |
35 | = xmmap (NULL, result.region_size, PROT_READ | PROT_WRITE, | |
36 | MAP_PRIVATE | MAP_ANONYMOUS, -1); | |
37 | /* Unmap the page after the allocation. */ | |
38 | xmprotect (result.region_start + (result.region_size - page_size), | |
39 | page_size, PROT_NONE); | |
40 | /* Align the allocation within the region so that it ends just | |
41 | before the PROT_NONE page. */ | |
42 | result.buffer = result.region_start + result.region_size - page_size - size; | |
43 | result.length = size; | |
44 | return result; | |
45 | } | |
46 | ||
47 | void | |
48 | support_next_to_fault_free (struct support_next_to_fault *ntf) | |
49 | { | |
50 | xmunmap (ntf->region_start, ntf->region_size); | |
51 | *ntf = (struct support_next_to_fault) { NULL, }; | |
52 | } |